U.S. patent number 11,239,076 [Application Number 16/815,682] was granted by the patent office on 2022-02-01 for film forming method and heat treatment apparatus.
This patent grant is currently assigned to TOKYO ELECTRON LIMITED. The grantee listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Hiroyuki Hayashi, Yutaka Motoyama.
United States Patent |
11,239,076 |
Motoyama , et al. |
February 1, 2022 |
Film forming method and heat treatment apparatus
Abstract
A film forming method includes forming an amorphous
semiconductor film on a recess, forming a first polycrystalline
semiconductor film by performing heat treatment on the amorphous
semiconductor film, and forming a second polycrystalline
semiconductor film on the first polycrystalline semiconductor film
formed by the heat treatment.
Inventors: |
Motoyama; Yutaka (Nirasaki,
JP), Hayashi; Hiroyuki (Nirasaki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
N/A |
JP |
|
|
Assignee: |
TOKYO ELECTRON LIMITED (Tokyo,
JP)
|
Family
ID: |
1000006086867 |
Appl.
No.: |
16/815,682 |
Filed: |
March 11, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200294800 A1 |
Sep 17, 2020 |
|
Foreign Application Priority Data
|
|
|
|
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Mar 13, 2019 [JP] |
|
|
JP2019-046357 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/0243 (20130101); H01L 21/02381 (20130101); H01L
21/02645 (20130101); H01L 21/02592 (20130101); H01L
21/02532 (20130101); H01L 21/3065 (20130101); H01L
21/02669 (20130101); H01L 21/02236 (20130101); H01L
21/67109 (20130101); H01L 21/02694 (20130101) |
Current International
Class: |
H01L
21/02 (20060101); H01L 21/67 (20060101); H01L
21/3065 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hoang; Quoc D
Attorney, Agent or Firm: Nath, Goldberg & Meyer Meyer;
Jerald L. Harkins; Tanya E.
Claims
What is claimed is:
1. A film forming method comprising: forming an amorphous
semiconductor film on a recess; forming a first polycrystalline
semiconductor film by performing heat treatment on the amorphous
semiconductor film; and after the first polycrystalline
semiconductor film is formed, forming a second polycrystalline
semiconductor film on the first polycrystalline semiconductor film
formed by the heat treatment.
2. The method of claim 1, wherein the forming the amorphous
semiconductor film comprises conformally forming the amorphous
semiconductor film.
3. The method of claim 1, further comprising etching the amorphous
semiconductor film such that a film thickness becomes larger at a
lower portion than an upper portion of the recess between the
forming the amorphous semiconductor film and the forming the first
polycrystalline semiconductor film.
4. The method of claim 3, wherein the forming the amorphous
semiconductor film, the etching, and the forming the first
polycrystalline semiconductor film are repeated a plurality of
times.
5. The method of claim 4, further comprising forming an inhibition
layer inhibiting crystal growth on a surface of the first
polycrystalline semiconductor film formed by the heat
treatment.
6. The method of claim 5, wherein the forming the inhibition layer
is a process of modifying the surface of the first polycrystalline
semiconductor film formed by the heat treatment.
7. The method of claim 5, wherein the forming the inhibition layer
is a process of oxidizing the surface of the first polycrystalline
semiconductor film formed by the heat treatment.
8. The method of claim 5, wherein the forming the inhibition layer
is a process of forming a film on the surface of the first
polycrystalline semiconductor film formed by the heat treatment
under a condition in which in-film hydrogen concentration is higher
than that of the forming the amorphous semiconductor film.
9. The method of claim 1, further comprising forming a seed layer
on the recess before the forming the amorphous semiconductor
film.
10. The method of claim 1, wherein the heat treatment is performed
at a temperature equal to or higher than a temperature of the
forming the amorphous semiconductor film.
11. The method of claim 1, wherein the forming the first
polycrystalline semiconductor film is performed at a same
temperature as a temperature of the forming the second
polycrystalline semiconductor film.
12. The method of claim 1, wherein the amorphous semiconductor film
is a film including at least one of silicon (Si) and germanium
(Ge).
13. A heat treatment apparatus comprising: a process container
accommodating a substrate having a recess on a surface of the
substrate; a gas supply supplying a processing gas into the process
container; a heater heating the substrate; and a controller,
wherein the controller controls the gas supply and the heater to
perform: forming an amorphous semiconductor film on the recess;
forming a first polycrystalline semiconductor film by performing
heat treatment on the amorphous semiconductor film; and after the
first polycrystalline semiconductor film is formed, forming a
second polycrystalline semiconductor film on the first
polycrystalline semiconductor film formed by the heat treatment.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2019-046357, filed on Mar. 13,
2019, the entire contents of which are incorporated herein by
reference.
TECHNICAL FIELD
The present disclosure relates to a film forming method and a heat
treatment apparatus.
BACKGROUND
A technology of forming a film to fill grooves such as holes or
trenches with a silicon film by alternately repeating film-forming
and etching to the grooves (see e.g., Patent Document 1) has been
known.
PRIOR ART DOCUMENT
[Patent Document] Japanese Patent Application Publication No.
2013-239717
SUMMARY
According to embodiments of the present disclosure, there is
provided a film forming method including forming an amorphous
semiconductor film on a recess, forming a first polycrystalline
semiconductor film by performing heat treatment on the amorphous
semiconductor film, and forming a second polycrystalline
semiconductor film on the first polycrystalline semiconductor film
formed by the heat treatment.
BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate embodiments of the present
disclosure, and together with the general description given above
and the detailed description of the embodiments given below, serve
to explain the principles of the present disclosure.
FIGS. 1A to 1E are process cross-sectional views showing a film
forming method according to a first embodiment.
FIGS. 2A and 2B are views illustrating the effect of the film
forming method of the first embodiment.
FIGS. 3A and 3B are views illustrating the effect of the film
forming method of the first embodiment.
FIGS. 4A to 4E are process cross-sectional views showing a film
forming method according to a second embodiment.
FIGS. 5A to 5G are process cross-sectional views showing a film
forming method according to a third embodiment.
FIGS. 6A to 6H are process cross-sectional views showing a film
forming method according to a fourth embodiment.
FIG. 7 is a view showing an example of a heat treatment apparatus
for performing the film forming method of an embodiment.
FIG. 8 is a view illustrating a process container of the heat
treatment apparatus of FIG. 7.
DETAILED DESCRIPTION
Reference will now be made in detail to various embodiments,
examples of which are illustrated in the accompanying drawings. In
the following detailed description, numerous specific details are
set forth in order to provide a thorough understanding of the
present disclosure. However, it will be apparent to one of ordinary
skill in the art that the present disclosure may be practiced
without these specific details. In other instances, well-known
methods, procedures, systems, and components have not been
described in detail so as not to unnecessarily obscure aspects of
the various embodiments.
Hereafter, a non-limiting exemplary embodiment of the present
disclosure is described with reference to the accompanying
drawings. The same or corresponding members or parts are given the
same or corresponding reference numerals throughout the
accompanying drawings and repeated description is omitted.
Film Forming Method
First Embodiment
A film forming method according to a first embodiment is described
with reference to FIGS. 1A to 1E. FIGS. 1A to 1E are process
cross-sectional views showing a film forming method according to
the first embodiment.
First, a substrate 101 having recesses 102 on the surface is
prepared (see FIG. 1A). The substrate 101 may be, for example, a
semiconductor substrate such as a silicon substrate. The recesses
102 may be, for example, trenches or holes. Further, an insulating
film such as a silicon oxide film (SiO.sub.2 film), a silicon
nitride film (SiN film) or the like may be formed on the surfaces
of the recesses 102.
Next, a seed layer 103 is formed on the substrate 101 by supplying
a silicon source gas for a seed layer to the substrate 101 (see
FIG. 1B). In an embodiment, the seed layer 103 may be formed using
aminosilane-based gas as the silicon source gas for the seed layer.
The aminosilane-based gas may be, for example, diisopropylamino
silane (DIPAS), tris(dimethylamino)silane (3DMAS), and
bis(tertiary-butylamino)silane (BTBAS). Further, the seed layer 103
may be formed using a high-order silane-based gas including two or
more silicon (Si) in one molecule as the silicon source gas for the
seed layer. The high-order silane-based gas may be, for example,
Si.sub.2H.sub.6, Si.sub.3H.sub.8, and Si.sub.4H.sub.10. Further,
the seed layer 103 may be formed using a silicon gas including a
hydrogenated silicon gas and a halogen-containing silicon gas as
the silicon source gas for the seed layer. The hydrogenated silicon
gas may be, for example, SiH.sub.4, Si.sub.2H.sub.6, and
Si.sub.3H.sub.8. The halogen-containing silicon gas may be, for
example, a fluorine-containing silicon gas such as SiF.sub.4,
SiHF.sub.3, SiH.sub.2F.sub.2, and SiH.sub.3F, chlorine-containing
silicon gas such as SiCl.sub.4, SiHCl.sub.3,
SiH.sub.2Cl.sub.2(DCS), and SiH.sub.3Cl, and a bromine-containing
silicon gas such as SiBr.sub.4, SiHBr.sub.3, SiH.sub.2Br, and
SiH.sub.3Br. Further, the seed layer 103 is not limited to any one
of the single layer films described above and may be a stacked film
formed by combining the substances described above. As the method
of forming the seed layer 103, for example, a Chemical Vapor
Deposition (CVD) method may be used. Further, when an
aminosilane-based gas is used as the silicon source gas for the
seed layer, a temperature at which thermal decomposition does not
occur is preferable. Since the seed layer 103 is formed on the
substrate 101 as described above, the roughness of an amorphous
silicon film 104 formed on the seed layer 103 can be reduced.
Further, the amorphous silicon film 104 to be described below may
be formed without forming the seed layer 103 on the substrate
101.
Next, the amorphous silicon film 104 is formed on the seed layer
103 by supplying a silicon source gas to the substrate 101 (see
FIG. 1C). In an embodiment, the amorphous silicon film 104 is
conformally formed on the seed layer 103 by supplying the silicon
source gas to the substrate 101, which has been heated to a
predetermined temperature (e.g., 550 degrees C.), through, for
example, a CVD method. The amorphous silicon film 104 may be a
non-doped silicon film or a silicon film doped with impurities. The
impurities may be, for example, boron (B), phosphorus (P), arsenic
(As), oxygen (O), and carbon (C). Gases that can be applied to the
CVD method may be used as the silicon source gas, and, for example,
any one or more combinations among a hydrogenated silicon gas, a
halogen-containing gas, and an aminosilane-based gas may be used.
The hydrogenated silicon gas may be, for example, SiH.sub.4,
Si.sub.2H.sub.6, and Si.sub.3H.sub.8. The halogen-containing
silicon gas may be, for example, fluorine-containing silicon gas
such as SiF.sub.4, SiHF.sub.3, SiH.sub.2F.sub.2, and SiH.sub.3F,
chlorine-containing silicon gas such as SiCl.sub.4, SiHCl.sub.3,
Si.sub.3Cl.sub.2(DCS), and SiF.sub.3Cl, and bromine-containing gas
such as SiBr.sub.4, SiHBr.sub.3, SiH.sub.2Br.sub.2, and
SiH.sub.3Br. The aminosilane-based gas may be, for example,
diisopropylamino silane (DIMS), tris(dimethylamino)silane (3DMAS),
and bis(tertiary-butylamino)silane (BTBAS). Further, when
impurities are doped. B.sub.2H.sub.6, BCl.sub.3, PH.sub.3, and
AsH.sub.3, for example, may be used as the impurity-containing
gas.
Next, a polycrystalline silicon film 105 is formed by
polycrystallizing the amorphous silicon film 104 by performing heat
treatment on the amorphous silicon film 104 by heating the
substrate 101 at a predetermined temperature (e.g., 600 degrees C.
or more) (see FIG. 1D). The heat treatment may be performed, for
example, in a vacuum atmosphere or an inert gas atmosphere, but it
is preferable that the heat treatment is performed in a hydrogen
atmosphere in order not to deteriorate the roughness of the silicon
film. Any temperature is possible as the predetermined temperature
as long as the amorphous silicon film 104 can be changed to a
polycrystalline silicon film. For example, the predetermined
temperature may be a temperature equal to or more than a
temperature at which the amorphous silicon film 104 is formed.
Further, it is preferable that the predetermined temperature is a
temperature that is substantially the same as the temperature of
the process of forming a polycrystalline silicon film 105 described
later. Accordingly, since there is no need to change the
temperature when the process proceeds to perform the process of
forming the polycrystalline silicon film 105 to be described below,
the time required for changing the temperature can be reduced,
thereby improving productivity.
Next, a polycrystalline silicon film 105 is formed to fill the
recesses 102 on the polycrystalline silicon film 105, which has
been polycrystallized by heat treatment by supplying the silicon
source gas to the substrate 101 (see FIG. 1E). In an embodiment,
the polycrystalline silicon film 105 is formed to fill the recesses
102 by supplying the silicon source gas to the substrate 101, which
has been heated to a temperature (e.g., COO degrees C. or higher)
higher than the temperature in the process of forming the amorphous
silicon film 104, through, for example, a CVD method.
According to the film forming method of the first embodiment
described above, the amorphous silicon film 104 is formed in the
recesses 102, the polycrystalline silicon film 105 is formed by
heat treatment, and then the polycrystalline silicon film 105 is
formed in the recesses 102 to fill the recesses 102. With this
configuration, since the recesses 102 are not filled when the
amorphous silicon film 104 is subjected to heat treatment, almost
no force is applied in the direction in which the width of the
recess 102 is reduced, even if hydrogen is desorbed from the
amorphous silicon film 104 by the heat treatment of the amorphous
silicon film 104 to allow film contraction. Accordingly, warpage of
the substrate 101 can be suppressed. Further, since the silicon
film filling the recesses 102 is polycrystalline, even if, for
example, the substrate 101 is exposed to a high temperature (e.g.,
700 degrees C. or more) in later processes, it is difficult for
hydrogen to be desorbed from the film. Accordingly, warpage of the
substrate 101 can be suppressed in later processes.
On the other hand, for example, when the recesses 102 of the
substrate 101 are filled with the amorphous silicon film 104 as
shown in FIG. 2A, the filling characteristics are good, but, as
shown in FIG. 2B, the substrate 101 becomes warped such that the
surface on which the amorphous silicon film 104 is formed becomes
convex. Further, for example, in later processes, when the
substrate 101 is exposed to a high temperature (e.g., 700 degrees
C. or more), the amorphous silicon film 104 is polycrystallized, so
that the polycrystalline silicon film 105 is formed. At this time,
as indicated by an arrow in FIG. 3A, a force is applied in the
direction in which the width of the recess 102 is reduced due to
desorption of hydrogen H.sub.2 from the film. Accordingly, as shown
in FIG. 3B, a severe warpage occurs in the substrate 101 in which
the surface on which the polycrystalline silicon film 105 is formed
in the recesses 102 becomes concave. When the substrate 101 becomes
severely warped as described above, it is difficult to move or
mount the substrate 101 to other places. Further, the larger the
ratio of the recesses 102 occupying the surface area is and the
larger the aspect ratio is, the more the substrate 101 bends.
On the other hand, in terms of reduction of warpage of the
substrate 101 only, it may be conceivable to form the
polycrystalline silicon film directly in the recesses 102. However,
when a substrate surface on which a polycrystalline silicon film is
formed is, for example, a surface of an insulating film and a
polycrystalline silicon film is directly formed on the substrate
surface, the film becomes a film with a very large surface
roughness, and accordingly, the filling characteristics are
degraded. Accordingly, warpage and filling are difficult to be
compatible with each other. However, as in the film forming method
of the first embodiment, a polycrystalline silicon film
polycrystallized through heat treatment after an amorphous silicon
film with a small roughness is formed can maintain a state of small
roughness. Further, polycrystalline silicon that is formed on the
polycrystalline silicon film with a small roughness can be formed
into a film while maintaining the small roughness. Accordingly, it
is possible to form a silicon film with good filling
characteristics.
Further, although a case in which the recesses 102 are filled with
a silicon film is described in the above example, the present
disclosure is not limited thereto. For example, the film forming
method can be applied even when the recesses 102 are filled with a
germanium film and a silicon germanium film. The germanium film and
the silicon germanium film may be, for example, non-doped films or
doped films.
When a germanium film is filled, for example, a germanium source
gas may be used instead of the silicon source gas. Further, for
example, a halogen-containing germanium gas may be used instead of
the halogen-containing silicon gas. Further, for example, a
hydrogenated germanium gas may be used instead of the hydrogenated
silicon gas. Further, for example, an aminogermanium-based gas may
be used instead of the aminosilane-based gas.
The halogen-containing germanium gas may include, for example,
fluorine-containing germanium gas such as GeF.sub.4, GeHF.sub.3,
GeH.sub.2F.sub.2, and GeH.sub.3F, a chlorine-containing germanium
gas such as GeCl.sub.4, GeHCl.sub.3, GeH.sub.2Cl.sub.2, and
GeH.sub.3Cl, and bromine-containing gas such as GeBr.sub.4,
GeHBr.sub.3, GeH.sub.2Br.sub.2, and GeH.sub.3Br. The hydrogenated
germanium gas may include, for example, GeH.sub.4, Ge.sub.2H.sub.6,
and Ge.sub.3H.sub.8. The aminogermanium-based gas may include, for
example, dimethylamino germane (DMAG), diethylamino germane (DEAG),
bis (dimethylamino germane (BDMAG), his (dimethylamino germane)
(BDEAG), and tris dimethylamino germane (3DMAG).
When a silicon germanium film is filled, for example, a silicon
source gas and a germanium source gas may be used instead of the
silicon source gas. Further, for example, a halogen-containing
silicon gas and a halogen-containing germanium gas may be used
instead of the halogen-containing silicon gas. Further, for
example, a hydrogenated silicon gas and a hydrogenated germanium
gas may be used instead of the hydrogenated silicon gas. Further,
for example, an aminosilane-based gas and an aminogermanium-based
gas may be used instead of the aminosilane-based gas.
Second Embodiment
A film forming method according to a second embodiment is described
with reference to FIGS. 4A to 4E. FIGS. 4A to 4E are process
cross-sectional views showing a film forming method according to
the second embodiment.
First, a substrate 201 having recesses 202 on the surface is
prepared (see FIG. 4A), The substrate 201 and the recesses 202 may
be the same as the substrate 101 and the recesses 102 in the first
embodiment. An insulating film such as a silicon oxide film
(SiO.sub.2 film) or a silicon nitride film (SiN film) may be formed
on the surfaces of the recesses 202.
Next, a seed layer 203 is formed on the substrate 201 by supplying
a silicon source gas for the seed layer to the substrate 201 (see
FIG. 4B). The method of forming the seed layer 203 may be the same
as the method of forming the seed layer 103 in the first
embodiment. Further, an amorphous silicon film 204 to be described
below may be formed without forming the seed layer 203 on the
substrate 201.
Next, the amorphous silicon film 204 is formed on the seed layer
203 by supplying the silicon source gas to the substrate 201. The
method of forming the amorphous silicon film 204 may be the same as
the method of forming the amorphous silicon film 104 in the first
embodiment.
Next, the amorphous silicon film 204 is etched such that the film
thickness becomes larger at the lower portions than the upper
portions of the recesses 202 by supplying a halogen-containing
etching gas to the substrate 201 (see FIG. 4C), Accordingly, the
opening at the upper portion of the recess 202 is widened. Further,
although a case in which the amorphous silicon film 204 remains on
the top surface of the recess 202 is shown in FIG. 4C, the top
surface of the recess 202 may be exposed. The halogen-containing
etching gas may include, for example, Cl.sub.2, HCl, F.sub.2,
Br.sub.2, HBr, and HI and may be a gas mixture thereof.
Next, a polycrystalline silicon film 205 is formed by
polycrystallizing the amorphous silicon film 204 by performing heat
treatment on the amorphous silicon film 204 by heating the
substrate 201 to a predetermined temperature (see FIG. 4D). The
condition of the heat treatment may be the same as the condition of
the heat treatment in the first embodiment.
Next, a polycrystalline silicon film 205 is formed to fill the
recesses 202 on the polycrystalline silicon film 205 poly
crystallized by the heat treatment by supplying the silicon source
gas to the substrate 201 and then performing heat treatment (see
FIG. 4E). The method of forming the polycrystalline silicon film
205 may be the same as the method of forming the polycrystalline
silicon film 105 in the first embodiment.
According to the film forming method of the second embodiment
described above, the amorphous silicon film 204 is formed on the
recesses 202, the polycrystalline silicon film 205 is formed by
heat treatment, and then the polycrystalline silicon film 205 is
formed on the recesses 202 to fill the recesses 202. Accordingly,
since the recesses 202 are not filled when the amorphous silicon
film 204 is subjected to the heat treatment, almost no force is
applied in the direction in which the width of the recesses 202 is
reduced, even if film contraction occurs due to desorption of
hydrogen from the film when performing the heat treatment on the
amorphous silicon film 204. Accordingly, warpage of the substrate
201 can be suppressed. Further, since the silicon film filling the
recesses 202 is polycrystalline, for example, in later processes,
even if the substrate 201 is exposed to a high temperature (e.g.,
700 degrees C. or more), desorption of hydrogen from the film
hardly occurs. Accordingly, warpage of the substrate 201 can be
suppressed in later processes.
Further, in the second embodiment, a process of etching the
amorphous silicon film 204 such that the film thickness becomes
larger at the lower portions than the upper portions of the
recesses 202 is performed between the process of forming the
amorphous silicon film 204 on the recesses 202 and the process of
performing the heat treatment on the amorphous silicon film 204.
Accordingly, the openings at the upper portions of the recesses 202
are widened, as compared with the case in which the process of
etching the amorphous silicon film 204 is not performed. Therefore,
it is possible to suppress a void or a seam that is generated in
the recesses 202 when the recesses 202 are filled with the
polycrystalline silicon film 205.
Third Embodiment
A film forming method according to a third embodiment is described
with reference to FIGS. 5A to 5G. FIGS. 5A to 5G are process
cross-sectional views showing the film forming method according to
a third embodiment.
First, a substrate 301 having recesses 302 on the surface is
prepared (see FIG. 5A). The substrate 301 and the recesses 302 may
be the same as the substrate 101 and the recesses 102 in the first
embodiment. An insulating film such as a silicon oxide film
(SiO.sub.2 film) or a silicon nitride film (SiN film) may be formed
on the surfaces of the recesses 302.
Next, a seed layer 303 is formed on the substrate 301 by supplying
a silicon source gas for the seed layer to the substrate 301 (see
FIG. 5B). The method of forming the seed layer 303 may be the same
as the method of forming the seed layer 103 in the first
embodiment. Further, an amorphous silicon film 304 to be described
below may be formed without forming the seed layer 303 on the
substrate 301.
Next, the amorphous silicon film 304 is formed on the seed layer
303 by supplying the silicon source gas to the substrate 301. The
method of forming the amorphous silicon film 304 may be the same as
the method of forming the amorphous silicon film 104 in the first
embodiment.
Next, the amorphous silicon film 304 is etched such that the film
thickness becomes larger at the lower portions than the upper
portions of the recesses 302 by supplying a halogen-containing
etching gas to the substrate 301 (see FIG. 5C). Accordingly, the
openings at the upper portions of the recess 302 are widened. The
method of etching the amorphous silicon film 304 may be the same as
the method of etching the amorphous silicon film 204 in the second
embodiment.
Next, a polycrystalline silicon film 305 is formed by
polycrystallizing the amorphous silicon film 304 by performing heat
treatment on the amorphous silicon film 304 by heating the
substrate 301 to a predetermined temperature (see FIG. 5D). The
condition of the heat treatment may be the same as the condition of
the heat treatment in the first embodiment.
Next, an amorphous silicon film 304 is formed on the
polycrystalline silicon film 305 by supplying the silicon source
gas to the substrate 301. The method of forming the amorphous
silicon film 304 may be the same as the method of forming the
amorphous silicon film 104 in the first embodiment.
Next, the amorphous silicon film 304 is etched such that the film
thickness becomes larger at the lower portions than the upper
portions of the recesses 302 by supplying halogen-containing
etching gas to the substrate 301 (see FIG. 5E). Accordingly,
V-shapes in which the upper portions of the recesses 302 are wide
and the lower portions of the recesses 302 are filled are formed.
The method of etching the amorphous silicon film 304 may be the
same as the method of etching the amorphous silicon film 204 in the
second embodiment.
Next, a polycrystalline silicon film 305 is formed by
polycrystallizing the amorphous silicon film 304 by performing heat
treatment on the amorphous silicon film 304 by heating the
substrate 301 to a predetermined temperature (see FIG. 5F). The
condition of the heat treatment may be the same as the condition of
the heat treatment in the first embodiment.
Next, a polycrystalline silicon film 305 is formed to fill the
recesses 302 on the polycrystalline silicon film 305
polycrystallized by the heat treatment by supplying the silicon
source gas to the substrate 301 (see FIG. 5G). The method of
forming the polycrystalline silicon film 305 may be the same as the
method of forming the polycrystalline silicon film 105 in the first
embodiment.
According to the film forming method of the third embodiment
described above, the amorphous silicon film 304 is formed on the
recesses 302, the polycrystalline silicon film 305 is formed by
heat treatment, and then the polycrystalline silicon film 305 is
formed on the recesses 302 to fill the recesses 302. Accordingly,
since the recesses 302 are not filled when the amorphous silicon
film 304 is subjected to the heat treatment, almost no force is
applied in the direction in which the width of the recesses 302 is
reduced, even if film contraction occurs due to desorption of
hydrogen from the film by the heat treatment of the amorphous
silicon film 304. Accordingly, warpage of the substrate 301 can be
suppressed. Further, since the silicon film filling the recesses
302 is polycrystalline, for example, in later processes, even if
the substrate 301 is exposed to a high temperature (e.g., 700
degrees C. or more), desorption of hydrogen from a film hardly
occurs. Accordingly, warpage of the substrate 301 can be suppressed
in later processes.
Further, in the third embodiment, the process of forming the
amorphous silicon film 304 on the recesses 302, the process of
etching the amorphous silicon film 304 such that the film thickness
becomes larger at the lower portions than the upper portions of the
recesses 302, and the process of performing the heat treatment on
the amorphous silicon film 304 are performed twice in this order.
Therefore, it is possible to particularly suppress a void or a seam
that is generated in the recesses 302 when the recesses 302 are
filled with the polycrystalline silicon film 305. Further, warpage
of the substrate 301 can be particularly suppressed in later
processes.
Further, a case in which a cycle that performs the process of
forming the amorphous silicon film 304, the process of etching the
amorphous silicon film 304, and the process of performing the heat
treatment on the amorphous silicon film 304 in this order is
repeated twice is described in the above example, but the present
disclosure is not limited thereto. For example, the cycle may be
performed three times or more. The number of the cycles may depend,
for example, on the shape of the recesses 302. For example, when
the shape of the recesses 302 is complicated, for example, when the
openings of the recesses 302 are narrow or the recesses 302 have a
barrel-shaped cross-sectional shape, it is preferable to perform
the cycle a plurality of times. Accordingly, it is possible to
suppress a void or a seam that is formed in the recesses 302.
Fourth Embodiment
A film forming method according to a fourth embodiment is described
with reference to FIGS. 6A to 6H. FIGS. 6A to 6H are process
cross-sectional views showing a film forming method according to
the fourth embodiment.
First, a substrate 401 having recesses 402 on the surface is
prepared (see FIG. 6A). The substrate 401 and the recesses 402 may
be the same as the substrate 101 and the recesses 102 in the first
embodiment. An insulating film such as a silicon oxide film
(SiO.sub.2 film) or a silicon nitride film (SiN film) may be formed
on the surfaces of the recesses 402.
Next, a seed layer 403 is formed on the substrate 401 by supplying
a silicon source gas for the seed layer to the substrate 401 (see
FIG. 6B). The method of forming the seed layer 403 may be the same
as the method of forming the seed layer 103 in the first
embodiment. Further, an amorphous silicon film 404 to be described
below may be formed without forming the seed layer 403 on the
substrate 401.
Next, the amorphous silicon film 404 is formed on the seed layer
403 by supplying the silicon source gas to the substrate 401. The
method of forming the amorphous silicon film 404 may be the same as
the method of forming the amorphous silicon film 104 in the first
embodiment.
Next, the amorphous silicon film 404 is etched such that the film
thickness becomes larger at the lower portions than the upper
portions of the recesses 402 by supplying a halogen-containing
etching gas to the substrate 401 (see FIG. 6C), Accordingly, the
openings at the upper portions of the recess 402 are widened. The
method of etching the amorphous silicon film 404 may be the same as
the method of etching the amorphous silicon film 204 in the second
embodiment.
Next, a polycrystalline silicon film 405 is formed by
polycrystallizing the amorphous silicon film 404 by performing heat
treatment on the amorphous silicon film 404 by heating the
substrate 401 to a predetermined temperature (see FIG. CD). The
condition of the heat treatment may be the same as the condition of
the heat treatment in the first embodiment.
Next, an inhibition layer 406 that inhibits crystal growth is
formed on the surface of the polycrystalline silicon film 405 (see
FIG. 6E). The inhibition layer 406 is formed, for example, by
performing a modifying treatment that modifies the surface of the
polycrystalline silicon film 405. The modifying treatment may be,
for example, a treatment that oxidizes the surface of the
polycrystalline silicon film 405 by supplying an oxidizer to the
substrate 401 or a treatment that forms a doped layer on the
surface of the polycrystalline silicon film 405 by supplying a
dopant to the substrate 401. The oxidizer may be, for example, an
oxidizing gas such as oxygen (O.sub.2) or a nitrous oxide
(N.sub.2O). The dopant may include, for example, a diborane
(B.sub.2H.sub.6) or phosphine (PH.sub.3) gas. Further, the
inhibition layer 406 may be formed, for example, by forming a film
that inhibits crystal growth on the surface of the polycrystalline
silicon film 405. The method of forming the film that inhibits
crystal growth may be, for example, a process of forming an
amorphous silicon film on the surface of the polycrystalline
silicon film 405 under a condition in which in-film hydrogen
concentration is higher than that in the process of forming the
amorphous silicon film 404 described above. For example, a
high-order hydrogenated silicon gas containing much more hydrogen
than the process of forming the amorphous silicon film 404 is used
as the silicon source gas. Further, a method of forming a film at a
temperature lower than that in the process of forming the amorphous
silicon film 404 may be also used. A method in which a
hydrogen-containing gas and a silicon source gas are supplied at
the same time may be also used.
Next, an amorphous silicon film 404 is formed on the inhibition
layer 406 by supplying the silicon source gas to the substrate 401.
The method of forming the amorphous silicon film 404 may be the
same as the method of forming the amorphous silicon film 104 in the
first embodiment.
Next, the amorphous silicon film 404 is etched such that the film
thickness becomes larger at the lower portions than the upper
portions of the recesses 402 by supplying a halogen-containing
etching gas to the substrate 401 (see FIG. 6F). Accordingly,
V-shapes in which the upper portions of the recesses 402 are wide
and the lower portions of the recesses 402 are filled are formed.
The method of etching the amorphous silicon film 404 may be the
same as the method of etching the amorphous silicon film 204 in the
second embodiment.
Next, a polycrystalline silicon film 405 is formed by
polycrystallizing the amorphous silicon film 404 by performing heat
treatment on the amorphous silicon film 404 by heating the
substrate 401 to a predetermined temperature see FIG. 6G). The
condition of the heat treatment may be the same as the condition of
the heat treatment in the first embodiment.
Next, a polycrystalline silicon film 405 is formed to fill the
recesses 402 on the polycrystalline silicon film 405
polycrystallized by the heat treatment by supplying the silicon
source gas to the substrate 401 (see FIG. 6H). The method of
forming the polycrystalline silicon film 405 may be the same as the
method of forming the polycrystalline silicon film 105 in the first
embodiment.
According to the film forming method of the fourth embodiment
described above, the amorphous silicon film 404 is formed on the
recesses 402, the polycrystalline silicon film 405 is formed by
heat treatment, and then the polycrystalline silicon film 405 is
formed on the recesses 402 to fill the recesses 402. Accordingly,
since the recesses 402 are not filled when the amorphous silicon
film 404 is subjected to the heat treatment, almost no force is
applied in the direction in which the width of the recesses 402 is
reduced, even if film contraction occurs due to desorption of
hydrogen from the film by the heat treatment of the amorphous
silicon film 404. Accordingly, warpage of the substrate 401 can be
suppressed. Further, since the silicon film filling the recesses
402 is polycrystalline, for example, in later processes, even if
the substrate 401 is exposed to a high temperature (e.g., 700
degrees C. or more), desorption of hydrogen from the film hardly
occurs. Accordingly, warpage of the substrate 401 can be suppressed
in later processes.
Further, in the fourth embodiment, the process of forming the
amorphous silicon film 404 on the recesses 402, the process of
etching the amorphous silicon film 404 such that the film thickness
becomes larger at the lower portions than the upper portions of the
recesses 402, and the process of performing the heat treatment on
the amorphous silicon film 404 are performed twice in this order.
Therefore, it is possible to particularly suppress a void or a seam
that is generated in the recesses 402 when the recesses 402 are
filled with the polycrystalline silicon film 405.
Further, in the fourth embodiment, the process of forming the
inhibition layer 406 which inhibits crystal growth on the surface
of the polycrystalline silicon film 405 formed by heat treatment is
performed between the process of firstly performing the heat
treatment on the amorphous silicon film 404 and the process of
secondly forming the amorphous silicon film 404. Accordingly, the
amorphous silicon film 404 can be easily formed even on the
polycrystalline silicon film 405 formed by heat treatment.
Therefore, since the silicon film that is etched in the etching
process is amorphous, etching can be performed with good roughness,
and accordingly, better filling can be performed.
Further, a case in which a cycle that performs the process of
forming the amorphous silicon film 404, the process of etching the
amorphous silicon film 404, and the process of performing heat
treatment on the amorphous silicon film 404 is repeated twice in
this order is described in the above example, but the present
disclosure is not limited thereto. For example, the cycle may be
performed three times or more. The number of the cycles may depend
on, for example, the shape of the recesses 402. For example, when
the shape of the recesses 402 is complicated, for example, when the
openings of the recesses 402 are narrow or the recesses 402 have a
barrel-shaped cross-sectional shape, it is preferable to perform
the cycle a plurality of times. Accordingly, it is possible to
suppress a void or a seam that is formed in the recesses 402.
[Heat Treatment Apparatus]
A heat treatment apparatus that can perform the above-described
film forming method is described by exemplifying a batch type
apparatus that performs heat treatment on a plurality of substrates
at once. However, the heat treatment apparatus is not limited to
the batch type apparatus. For example, a single wafer type
processing apparatus that processes substrates one by one may be
used. Further, for example, a semi-batch type apparatus that forms
a film on a substrate by passing the substrate sequentially through
a region in which a source gas is supplied and a region in which a
reacting gas reacting with the source gas is supplied, by revolving
a plurality of wafers disposed on a rotary table in a process
container may be used.
FIG. 7 is a view showing an example of a heat treatment apparatus
for performing the film forming method of an embodiment. FIG. 8 is
a view illustrating a process container of the heat treatment
apparatus of FIG. 7.
As shown in FIG. 7, a heat treatment apparatus 1 includes a process
container 34, a cover 36, a wafer boat 38, a gas supply 40, an
exhauster 41, and a heater 42.
The process container 34 is a process container that accommodates
the wafer boat 38. The wafer boat 38 is a substrate holder that
holds a plurality of semiconductor wafers (hereafter, referred to
as wafers W) with predetermined separations. The process container
34 has an inner tube having a cylindrical shape with a ceiling and
an open lower end, and an outer tube 46 having a cylindrical shape
with a ceiling, which covers the outer side of the inner tube 44,
and an open lower end. The inner tube 44 and the outer tube 46 are
made of a heat resistance material such as quartz and are coaxially
disposed to form a double tube structure.
The ceiling 44A of the inner tube 44 is formed, for example, to be
flat. A nozzle accommodation part 48 which accommodates a gas
supply pipe is formed at a side of the inner tube 44 along the
longitudinal direction (vertically). For example, as shown in FIG.
8, a protruding portion 50 is formed by protruding a portion of the
side wall of the inner tube 44 in an outward direction and the
inside of the protruding portion 50 functions as the nozzle
accommodation part 48. A rectangular opening 52 having a width L1
is formed in the longitudinal direction (vertically) on the
opposite side of the inner tube 44 to the nozzle accommodating part
48, facing the nozzle accommodation part 48.
The opening 52 is a gas exhaust hole formed to be able to discharge
the gas in the inner tube 44. The opening 52 vertically extends
such that the length thereof is the same as the length of the wafer
boat 38 or larger than the length of the wafer boat 38. That is,
the upper end of the opening 52 is positioned higher than the
position corresponding to the upper end of the wafer boat 38 and
the lower end of the opening 52 extends to be positioned lower than
the position corresponding to the lower end of the wafer boat 38.
In detail, as shown in FIG. 7, the distance L2 in the height
direction between the upper end of the wafer boat 38 and the upper
end of the opening 52 is in the range of about 0 mm to 5 mm.
Further, the distance L3 in the height direction between the lower
end of the wafer boat 38 and the lower end of the opening 52 is in
the range of about 0 mm to 350 mm.
The lower end of the process container 34 is supported by a
cylindrical manifold 54 that is made of, for example, stainless
steel. A flange 56 is formed at the upper end of the manifold 54
and the lower end of the outer tube 46 is installed and supported
on the flange 56. A sealing member 58 such as an O-ring is disposed
between the flange 56 and the lower end of the outer tube 46,
thereby making the inside of the outer tube 46 hermetic.
A circular ring-shaped support 60 is formed on the inner wall of
the upper portion of the manifold 54 and the lower end of the inner
tube 44 is installed and supported on the support 60. The cover 36
is hermetically installed in the opening of the lower end of the
manifold 54 while disposing a sealing member 62 such as an O-ring
between them, and the opening of the lower end of the process
container 34, that is, the opening of the manifold 54, is
hermetically closed. The cover 36 is made of, for example,
stainless steel.
A rotary shaft 66 passes through the center of the cover 36 via a
magnetic fluid sealing part 64. The lower portion of the rotary
shaft 66 is rotatably supported by an arm 68A of an elevator 68
which is a boat elevator.
A rotary plate 70 is disposed at the upper end of the rotary shaft
66 and the wafer boat 38 holding the wafer W is loaded on the
rotary plate 70 through a heat-retention table 72 made of quartz.
Accordingly, when the elevator 68 is moved up/down, the cover 36
and the wafer boat 38 are integrally moved up/down, so that the
wafer boat 38 can be easily inserted and separated with respect to
the inside of the process container 34.
The gas supply 40 is disposed at the manifold 54 and introduces a
film-forming gas, a processing gas such as an etching gas, or a
purge gas into the inner tube 44. The gas supply 40 has a plurality
of (e.g., three) gas supply pipes 76, 78, and 80 made of quartz.
The gas supply pipes 76, 78, and 80 are disposed longitudinally in
the inner tube 44, and the base ends are bent in an L-shape and
supported through the manifold 54.
The gas supply pipes 76, 78, and 80, as shown in FIG. 8, are
installed in a line in the circumferential direction in the nozzle
accommodation part 48 of the inner tube 44. A plurality of gas
holes 76A, 78A, and 80A are formed with predetermined separations
in the gas supply pipes 76, 78, and 80 in the longitudinal
direction, respectively, such that gases can be discharged
horizontally through the gas holes 76A, 78A, and 80A. For example,
the predetermined separations are set to be the same as the
separations of wafers W supported by the wafer boat 38. Further,
the position in the height direction is set such that the
respective gas holes 76A, 78A, and 80A are positioned in the middle
between wafers W vertically adjacent to one another, so that gases
can be efficiently supplied to the spaces between the wafers W. The
film-forming gas, the etching gas, and the purge gas are used as
the gases, and the gases can be supplied through the gas holes 76A,
78A, and 80A, if necessary, while the flow rates are
controlled.
A gas outlet 82 is formed in the side wall of the upper portion of
the manifold 54 over the support 60, so the gas in the inner tube
44 discharged from the opening 52 through the space 84 between the
inner tube 44 and the outer tube 46 can be discharged. The
exhauster 41 is disposed at the gas outlet 82. The exhauster 41 has
an exhaust passage 86 connected to the gas outlet 82, and a
pressure control valve 88 and a vacuum pump 90 are sequentially
installed in the exhaust passage 86, so that the inside of the
process container 34 can be evacuated.
The cylindrical heater 42 is disposed outside the outer tube 46 to
cover the outer tube 46. The heater 42 heats the wafers W
accommodated in the process container 34.
A general operation of the heat treatment apparatus 1 is controlled
by a controller 95. The controller 95 may be, for example, a
computer, etc. Further, programs of the computer that performs the
general operation of the heat treatment apparatus 1 are stored in a
memory medium 96. The memory medium 96 may be, for example, a
flexible disk, a compact disc, a hard disk, a flash memory, and a
DVD.
An example of a filling method of semiconductor film in a wafer W
having recesses on the surface of the wafer W by the heat treatment
apparatus 1 is described. First, the wafer boat 38 holding a
plurality of wafers W is loaded into the process container 34 by
the elevator 68 and the opening of the lower end of the process
container 34 is hermetically closed by the cover 36. Next, the
operations of the gas supply 40, the exhauster 41, the heater 42,
etc. are controlled by the controller 95 to perform the methods of
forming a film of the first to fourth embodiments described above.
Accordingly, it is possible to form a semiconductor film having a
good filling characteristic while reducing warpage of the wafers
W.
Further, in the embodiments, the amorphous silicon films 104, 204,
304, and 404 are examples of an amorphous semiconductor film and
the polycrystalline silicon films 105, 20.5, 305, and 405 are
examples of a polycrystalline semiconductor film.
The case in which a substrate is a semiconductor substrate is
exemplified in the above embodiments, but the present disclosure is
not limited thereto. For example, the substrate may be a large
substrate for a Flat Panel Display (FPD) or a substrate for an EL
device or a solar cell.
According to the present disclosure, it is possible to form a
semiconductor film having good filling characteristics while
reducing warpage of a substrate.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the disclosures. Indeed, the embodiments
described herein may be embodied in a variety of other forms.
Furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the disclosures. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
disclosures.
* * * * *